A new method of factor analysis has been devised as a dynamic study in nuclear medicine. Instead of whole sequence factor analysis of images, partially-sequenced images of Kr-81m pulmonary ventilation scintigrams, acquired with respiratory-gated signals, were analysed using this method. Incrementing the first and last frame number of the image sequence, the motion of the factor images, was obtained including diaphragmatic images, thoracic images and physiological pathological dead space, during one respiratory cycle. The varying form of the correlation between two factor images over time provided a distinguishable pattern of patients with pathological conditions such as chronic obstructive pulmonary disese from normal subjects.